I. Field of the Invention
The present invention relates to road markers for reflecting the light of oncoming vehicles. More particularly, the present invention relates to snowplowable road markers.
II. Background of &he Invention
Road markers are known for marking traffic lanes and controlling the f low of traffic. Typically, the road markers have a body molded of plastic material and include one or more reflectors to return the light from headlights of oncoming vehicles. The plastic bodies are mounted directly on the top surface of the road as disclosed in U.S. Pat. No. 4,753,548.
However, in geographic areas where there is sufficient snow fall to require the use of snowplows to remove the snow, it has been found that snowplow blades frequently damage road markers or remove the markers from the road. To overcome this problem, it is known, such as disclosed in U.S. Pat. No. 3,587,416, to form a metal casting having a pair of spaced apart ramps mounted in the roadway surface. A cube corner reflector is mounted in the casting between the pair of ramps so that a snowplow blade will ride up the ramps and pass over the reflector without damaging the reflector.
It is also known, as disclosed in U.S. Pat. No. 4,577,992, to form a circular casting having a dished top surface with a channel extending across the top surface so that a snowplow blade is deflected by the dished top surface regardless of the angle from which the snowplow blade engages the top surface.
Likewise, U.S. Pat. No. 4,402,628 discloses a circular sheet metal base having a raised protected cross-rib extending between a pair of raised side members. The protective rib extends between a pair of markers which are disposed in channels extending radially from each side of the rib.
Because tires of vehicles frequently pass over the snowplowable road markers, it is advantageous to minimize the height of the road marker extending above the road surface to minimize the disturbance to the handling of the vehicle when passing over the road markers. Additionally, previously known snowplowable markers frequently are removed from the road or damaged by contact with snowplow blades. It has been found that snowplow blades will slice through the hardened steel pavement markers such as disclosed in U.S. Pat. No. 4,402,628. Likewise, it has been found that snowplow blades may ride under the peripheral edge of markers such as disclosed in U.S. Pat. No. 4,577,992 and remove the casting from the road.